Preparation of mixed polyvinyl esters



Patented Nov. 13, 1951 PREPABATIQN. OF'MIXEDJROLYVINYL, ESTERS' n Hyman Rudolf, Springfield, Massz, assigncrto. Shawinigani Resins Corporation, Springfield, Mass-i, a; corporationofv Massachusetts NoDrawing; Applicationllecember"2m 1947;

Serial No. 794:123-

6:1Glaims. (Cl. 260-23):

1.; This invention: relatesrto: mixed esters of-polyivinyl'alcohol.

It: is known to prepare mixedzesters. of poly-s vinyl alcohol by copolymeriz-ingtwo-ormorevinyl esters of' carboxyl'ic acids;

estersv in this mannersand' it:- would beadvanta geous incertain instances to have. another methad for preparing arch-products.

It is an object: of this: inyentionator provide. a

new-method for: preparing mixed esters of poly vinyl alcohol.v A. further: object is: to provide a.

process for preparing mixed esters? of... polyvinyl alcohol directly from; polyvinyl esters of 'carboxylicv acids.

These and, otherrobjects; are attained according to this inventiomby reacting-polyvinyl estersof carboxylic acids with anzacylatmgagentyfrom thegroup consisting of anhydrides of, earboxylic organic acids and, acyl chlorides.whiohxare-resistant: to decomposition by alkalr-undenconditions of, the reaction, in the presence. ofan aqueous solution of analkali metalrhiidroxidetand':aasol+ vent.

Thefollowing examples are illustrative of the present invention but; are not to; .bezconstruedi as limitatiye thereor. Where parts. are: mentioned; they :are; parts; by'weightr.

Example! A solution of. 86 parts (.1 molecular proportion)- of polyvinyl acetate, GSO-partsbr dioxan'e; and 70 parts (0.5 molecular proportion) of benzyl chloride is prepared. To this solution there are slowly addedawith vigorous: agitationAQr parts: (1 molecular proportion) -01? sodium: hydroxide? dis solved an equal amount-of water while mains taining the reaction mixture at about room tern?- perature. Thev reactiommixturethen: stirred at room temperature for. about-2.15 hours; Water is added to the resulting product and thoroughly kneaded therewith; The product is-then dissolved in ethanol, reprecipitatedby the addition of'water and separatedfrom the liquid 'medium. Afterremating the solution; reprecipitationaandseparation from the li'quid med'i u-m; the productis-dried by heating under vacuum at about 40 0.; fol lowed by heating at" 120 C. at 'atmospheric pressure. Asa result of this; treatment: about: 80 parts of an amber-colored" product" is" obtained. Analysis of" this product showsthatitcontains 355% benzoategroups by'weight, calculated as polyvinyl benzoa-te, polyvinyl alcohol, and the balance substantially polyvinyl; aceta-tcn It. is found that this mixed ester-- of polyvinyl"alcohol However; there are certain difiiculties involved in" preparing" mixed may be" easily molded-under heating and-pres sure; into light-colored, flexible, transparent. sheets.

Example II;

Example'l'is'repeated except that the reaction mixture isagitated at about 30 C. for 48 hours. The resulting product purified in the same manner as the product in Example I, is found to contain 22.4% b-enzoate groups by weight, calculated a polyvinyl benzoate, 0% polyvinyl alcohol and the balance; substantially polyvinyl acetate. This product,- like the product of Example .I,. is easily molded under heating and pressure into light-colored, transparentflexible sheets.

Example. III

Example I is'repeated except that the reaction mixture is agitated in a dough-type mixer at 30-45 C: foraboutthree hours. In this case the product is purified by successively dissolving the product in ethanol and then precipitating the product with isopropyl ether. The mixed ester which results is found to contain 12.6% benzoate groups, calculated as polyvinyl benzoate, the bal-- ance substantially polyvinyl acetate and to be substantially'free from hydroxyl groups.

From the foregoing examples, which are illustrative of the present invention, it can readily be seen'that the present invention provides an unexpectedly valuablemethod' for preparing mixed esters of polyvinyl alcohol. For example, it is to be noted that it is not necessary to hydrolyze the polyvinyl ester in a separate step but by means of the one step of the invention, acetate or other ester groups are directly replaced with ester groups" of a difierentnature.

Numerous'variations may be introduced in the process of," the invention as exemplified by the examples: Thus, in place of polyvinyl acetate other polymers of vinyl esters of carboxylic acids may be used, as for example, polyvinyl formate, polyvinyl propionate, polyvinyl butyrate, polyvinyl valerate, polyvinyl hexoate and other polyvinyl estersin which the acyl groups are derived from organic acids, e. g., the acylgroups'of the acylating'agents set forth below; A preferred group of'polyvinyl esters is that in which the acyl group; is derived from a lower aliphatic acid, i. 'e.', an aliphatic acid" containing 1-6 carbon atomssuch as those mentioned above.

The polyvinyl acetateused in the examples is characterized by-such a degree of polymerization as to have a-viscosi ty-of aboutv20 centipoisesirr a l+molar benzene solutionat 20 C. Polyvinyl acetates exhibiting-other. viscosity characterisithe lower aliphatic acyl chlorides are not suitable for the purpose of the invention. However, higher aliphatic acyl chlorides, i. e., those which contain 10 or more carbon atoms may be used asa well as aromatic acid chlorides. Examples of acid chlorides which may be used include the chlorides of the following acids: decanoic acid, I

dodecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, phthalic acid, benzoic acid, toluic acids,- diphenic acid, o-benzylbenzoic acid, naphthoic acids, naphthalene dicarboxylicacids and the like as well as substitution products such as those mentioned below in the case of the anhydrides. When desired, mixtures of these and/or other acid chlorides may be used.

The following are examples of anhydrides.

which may be used as acylating agents in the process of the invention: aliphatic anhydrides, such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, nonanoic anhydride, decanoic anhydride, dodecanoic anhydride, hexadecanoic anhydride, octadecanoic anhydride, eicosanoic anhydride, aromatic acid anhydrides such as phthalic anhydride, benzoic anhydride, toluic anhydride, phenyl acetic anhydride, phenyl propionic anhydride, phenyl butvric anhydride, diphenic anhydride, o-benzyl benzoic anhydride, naphthoic anhydride, naphthalene dicarboxylic acid anhydrides, and the like as Well as substitution products thereof, e. g., halo, i. e., chloro, bromo or fluoro derivatives, alkyl, 1. e., methyl, ethyl, propyl, butyl, pentvl, hexyl derivatives and the like. Mixed anhydrides may be used when desired based on any combination of the above or other anhydrides. Also mixtures of these and/ or other anhydrides may be used.

In place of sodium hydroxide other alkali metal hydroxides may be used in the process of the invention, as for example, potassium hydroxide, cesium hydroxide and rubidium hydroxide.

In place of dioxane other liquids may be employed which are solvents for both the initial polyvinyl ester and the mixed ester prepared therefrom. Examples of other suitable solvents include: benzene, toluene, xylene, etc.

The temperature at which the reaction is conducted may be substantially varied. However, it is usually preferred that temperatures of not over 60 be employed to avoid undesirable side reaction. The duration of the reaction is governed by the relative proportions of the ingredients employed and the results desired. Thus, under certain circumstances it may be desirable to continue the reaction until equilibrium is established while under other circumstances it may be preferred to employ an excess of the acylating agent and stop the reaction when the desired degree of replacement of ester groups has occurred.

The relative proportions of polyvinyl ester, acylating agent and alkali metal hydroxide may be substantially varied. Usually, it is found desirable to employ a substantial excess of acylating agent in order to promote a rapid reaction.

For example, up to a 200-500% excess of the acylating agent based on the desired degree of ester replacement is found to be advantageous. Sufficient alkali metal hydroxide should be used to be equivalent to twice the desired degree of ester replacement. Larger amounts may be used, for example, up to a ZOO-500% excess over the above amount. The concentration of the aqueous solution of the alkali metal hydroxide may be substantially varied. For example, a 5-60% solution may be used.

The amount of solvent which is used may be substantially varied. Preferably, the amount used is suflicient to keep the reactants and the products in,solution throughout the reaction.

- An excessive amount is usually avoided for economic reasons.

As indicated above, the extent of the reaction may be substantially varied by variation in the reaction conditions and duration. While replacement of as little as 1% of the acyl groups of the polyvinyl esters by other acyl groups may be effective to alter materially the characteristics thereof and is intended to be covered by the present invention, usually it is found that the more valuable products do not contain less than 5% (based on total acyl group content) of any particular acyl group. Thus, while it is contemplated that the process of the invention may be used to replace 1-99% of the acyl groups of a polyvinyl ester with other acyl groups, usually the degree of replacement is 5-95%.

It is obvious that many variations may be mad in the processes and products of this invention without departing from the spirit and scope thereof as defined in the appended claims. I

What is claimed is:

l. A process which comprises reacting a homopolymer of a vinyl ester of an unsubstituted aliphatic monocarboxylic acid having 1-6 carbon atoms with an acylating agent having only carboxyl functional groups and an acyl group differ ent from the acyl group of the polyvinyl ester, the acylating agent being a member of the group consisting of aromatic carboxylic acid chlorides, aliphatic carboxylic acid chlorides containing more than 9 but less than 21 carbon atoms, and organic carboxylic acid anhydrides, in the presence of an aqueous solution of an alkali metal hydroxide of from 5% to 60% concentration and an inert organic solvent for the vinyl ester, and continuing said reaction until a' mixed ester of polyvinyl alcohol is formed in which from 1% to 99% of the initial ester groups have been replaced with the ester groups from the acylating agent, said mixed ester being free from polyvinyl alcohol groups.

2. A process as defined in claim 1 in which the acylating agent is an organic carboxylic acid anhydride.

3. A process as defined in claim 2 in which the anhydride is an aromatic acid anhydride.

4. A process as defined in claim 1 in which the acid chloride is an aliphatic carboxylic acid chloride containing more than 9 but less than 21 carbon atoms.

5. A process for preparing a mixed ester of polyvinyl alcohol which comprises reacting poly! vinyl acetate with benzoyl chloride in the pres-. ence of an aqueous solution of sodium hydroxide of 5% to 60% concentration and dioxane until 1% to 99% of the acetate groups are replaced with benzoate groups, said mixed ester being free from polyvinyl alcohol groups.

, 5 6 6. A process as defined in claim 5 in which the reaction is continued until 5% to 95% 0f the FOREIGN PATENTS acetate groups are replaced by benzoate groups. Number Country Date HYMAN RUDOFF- 396,186 Great Britain Aug. 3, 193? REFERENCES CITED OTHER REFERENCES The following references are of record in the Weygand: Organic Preparations, Interscience, file of this patent: 1945. pp- 180,

UNITED STATES PATENTS 10 Number Name Date 2,145,345 Dreyfus Jan. 31, 1939 2,269,187 DAlelio Jan. 6, 1942 

1. A PROCESS WHICH COMPRISES REACTING A HOMOPOLYMER OF A VINYL ESTER OF AN UNSUBSTITUTED ALIPHATIC MONOCARBOXYLIC ACID HAVING 1-6 CARBON ATOMS WITH AN ACYLATING AGENT HAVING ONLY CARBOXYL FUNCTIONAL GROUPS AND AN ACYL GROUP DIFFERENT FROM THE ACYL GROUP OF THE POLYVINYL ESTER, THE ACYLATING AGENT BEING A MEMBER OF THE GROUP CONSISTING OF AROMATIC CARBOXYLIC ACID CHLORIDES, ALIPHATIC CARBOXYLIC ACID CHLORIDES CONTAINING MORE THAN 9 BUT LESS THAN 21 CARBON ATOMS, AND ORGANIC CARBOXYLIC ACID ANHYDRIDES, IN THE PRESENCE OF AN AQUEOUS SOLUTION OF AN ALKALI METAL HYDROXIDE OF FROM 5% TO 60% CONCENTRATION AND AN INERT ORGANIC SOLVENT FOR THE VINYL ESTER, AND CONTINUING SAID REACTION UNTIL A MIXED ESTER OF POLYVINYL ALCOHOL IS FORMED IN WHICH FROM 1% TO 99% OF THE INITIAL ESTER GROUPS HAVE BEEN REPLACED WITH THE ESTER GROUPS FROM THE ACYLATING AGENT, SAID MIXED ESTER BEING FREE FROM POLYVINYL ALCOHOL GROUPS. 